[DSL] Added an integration test for the "match phrase prefix" query

Related: #448

Author: karmi

test/integration/search_query_test.rb

@@ -25,6 +25,14 @@ class QueryIntegrationTest < ::Elasticsearch::Test::IntegrationTestCase
           end
         end
 
+        context "for match_phrase_prefix query" do
+          should "find the document" do
+            response = @client.search index: 'test', body: search { query { match_phrase_prefix title: 'te' } }.to_hash
+
+            assert_equal 1, response['hits']['total']
+          end
+        end
+
         context "for query_string query" do
           should "find the document" do
             response = @client.search index: 'test', body: search { query { query_string { query 'te*' } } }.to_hash